Ron Paul suspends his US presidential campaign

"We will no longer spend resources campaigning in primaries in states that have not yet voted. Doing so with any hope of success would take many tens of millions of dollars we simply do not have," Paul said in an email to his supporters on Monday.

However, Paul said his campaign will continue to work in the state convention process.

"We will continue to take leadership positions, win delegates, and carry a strong message to the Republican National Convention that Liberty is the way of the future," he wrote.

In his letter, Paul promises to lay out the campaign's delegate strategy for the Republican National Convention and asks supporters to "stay tuned" for further strategy updates.

"I hope all supporters of Liberty will remain deeply involved -- become delegates, win office, and take leadership positions. I will be right there with you. In the coming days, my campaign leadership will lay out to you our delegate strategy and what you can do to help, so please stay tuned," he said.

So far Paul has just 99 delegates as compared to 949 of Romney, who is falling little short of required 1,144 delegates required to formally become the Republican presidential candidate.